SLVSE09A April   2017  – April 2017 TPS61096A

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 ESD Ratings
    2. 6.2 Recommended Operating Conditions
    3. 6.3 Thermal Information
    4. 6.4 Electrical Characteristics
    5. 6.5 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Controller Circuit
      2. 7.3.2 Current Limit Selection
    4. 7.4 Device Functional Modes
      1. 7.4.1 Under-Voltage Lockout
      2. 7.4.2 Enable and Disable
      3. 7.4.3 Soft Start
      4. 7.4.4 Level Shifters
      5. 7.4.5 Over-voltage Protection
      6. 7.4.6 Thermal Shutdown
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Custom Design With WEBENCH® Tools
        2. 8.2.2.2 Programming the Output Voltage
        3. 8.2.2.3 Maximum Output Current
        4. 8.2.2.4 Inductor Selection
        5. 8.2.2.5 Capacitor Selection
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
      2. 11.1.2 Development Support
        1. 11.1.2.1 Custom Design With WEBENCH® Tools
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

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8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

8.1 Application Information

The TPS61096A is a high output voltage boost converter with ultra-low quiescent current. It is designed for products powered by either two-cell alkaline, or one cell Li-Ion or Li-polymer battery, for which high efficiency under light load condition is critical to achieve long battery life operation. It can also support selective inductor peak current. With lower current limit, the TPS61096A can reduce inductor ripple so as to reduce external components size for light load applications. With higher current limit, the TPS61096A can have higher output current capability to meet more application requirements.

The TPS61096A integrates two-channel low-power level shifters to convert low level signals to output voltage signals for specific applications.

8.2 Typical Application

TPS61096A Typ_app_12V_pulse_SLVSE09.gif Figure 13. 12-V Pulse Generation From 3.6-V Input Voltage

8.2.1 Design Requirements

In this typical application, two channel 50-kHz pulse signals of 3.2 V amplitude are output from a controller, and the signals' amplitude is required to be converted. High efficiency under light load is required.

The TPS61096A converts the 3.6-V input voltage to 12-V output voltage first, and this 12-V output voltage provides bias to the integrated two level shifters. The level shifters outputs have no load so the boost converter always works in light load condition.

Table 1. TPS61096A Design Parameters

PARAMETER EXAMPLE VALUES
Input voltage 3.6 V
Output voltage 12 V
Input pulse frequency 50 kHz
Input pulse duty cycle 50%
Input pulse amplitude 3.2 V
Output pulse frequency and duty cycle Same as input pulse
Output pulse amplitude 12 V
Output load of level shifters No load

8.2.2 Detailed Design Procedure

The following sections describe the selection process of the external components.

8.2.2.1 Custom Design With WEBENCH® Tools

Click here to create a custom design using the TPS61096A device with the WEBENCH® Power Designer.

  1. Start by entering the input voltage (VIN), output voltage (VOUT), and output current (IOUT) requirements.
  2. Optimize the design for key parameters such as efficiency, footprint, and cost using the optimizer dial.
  3. Compare the generated design with other possible solutions from Texas Instruments.

The WEBENCH Power Designer provides a customized schematic along with a list of materials with real-time pricing and component availability.

In most cases, these actions are available:

  • Run electrical simulations to see important waveforms and circuit performance
  • Run thermal simulations to understand board thermal performance
  • Export customized schematic and layout into popular CAD formats
  • Print PDF reports for the design, and share the design with colleagues

Get more information about WEBENCH tools at www.ti.com/WEBENCH.

8.2.2.2 Programming the Output Voltage

By selecting the external resistor divider R1 and R2, as shown in Equation 1, the output voltage is programmed to the desired value. When the output voltage is regulated, the typical VREF voltage at FB pin is 1.0 V.

Equation 1. TPS61096A Eq_Vout_SLVSDB2.gif

For the best accuracy, the current following through R2 should be 100 times larger than FB pin leakage current. Changing R2 towards a lower value increases the robustness against noise injection while has little influence on efficiency at light load, because TPS61096A only samples FB voltage when it is lower than the reference. 110-kΩ and 10-kΩ resistors are selected for R1 and R2. High accuracy resistors are recommended for better output voltage accuracy.

8.2.2.3 Maximum Output Current

The maximum output capability of the TPS61096A is determined by the input voltage to output voltage ratio and the current limit of the boost converter. It can be estimated by Equation 2.

Equation 2. TPS61096A Eq_Iout(max)_SLVSDB2.gif

where

  • VIN is the input voltage
  • VOUT is the output voltage
  • ILIM is the peak current limit
  • η is the power conversion efficiency

If an application requires high output current capability of the boost converter, ILIM pin should be tied to logic high voltage to enable a higher current limit. Minimum input voltage, maximum boost output voltage and minimum value of the selected current limit should be used as the worst case condition for the estimation.

In this example, the output load is only the bias current to the level shifters, so it will not reach the maximum output current value.

8.2.2.4 Inductor Selection

Because the PFM peak current control scheme is inherently stable, the inductor value does not affect the stability of the regulator. The selection of the inductor together with the nominal load current, input and output voltage of the application determines the switching frequency of the converter. Depending on the application, inductor values from 1.0 μH to 47 μH are recommended.

The inductor value determines the maximum switching frequency of the converter. Therefore, select the inductor value that ensures the maximum switching frequency at the converter maximum load current does not exceed the required maximum switching frequency. The maximum switching frequency is calculated by Equation 3:

Equation 3. TPS61096A Eq_fs(max)_SLVSDB2.gif

where

  • L is the selected inductor value

Choose the smaller one between VIN(max) and TPS61096A Eq_n_Vout_SLVSDB2.gif to calculate the highest switching frequency across the entire input range.

The selected inductor should have a saturation current that is larger than the maximum peak current of the converter. Use the minimal value of selected current limit for this calculation.

Another important inductor parameter is the dc resistance. The lower the dc resistance, the higher the efficiency of the converter. Table 2 lists the recommended inductors for the TPS61096A.

Table 2. Recommended Inductors

INDUCTANCE (µH) ISAT (A) DC RESISTANCE (mΩ) PACKAGE SIZE PART NUMBER MANUFACTURER(1)
2.2 1.7 117 2.0 mm × 1.6 mm DFE201610E-2R2M=P2 TOKO
2.2 1.5 106 3.2 mm × 2.5 mm 74479299222 Wurth
2.2 0.7 200 2.0 mm × 1.2 mm 74479775222A Wurth
(1) See Third-Party Products disclaimer

8.2.2.5 Capacitor Selection

For best output and input voltage filtering, low ESR X5R or X7R ceramic capacitors are recommended.

The input capacitor minimizes input voltage ripple, suppresses input voltage spikes and provides a stable system rail for the device. An input capacitor value of 4.7 μF is normally recommended to improve transient behavior of the regulator and EMI behavior of the total power supply circuit. A ceramic capacitor placed as close as possible to the VIN and GND pins of the IC is recommended.

The selection of output capacitor determines the output voltage ripple. The default hysteresis window of Vout is 30mV, but due to the 10-µs internal comparator delay, output ripple gets larger as load gets heavier. The output ripple is calculated with Equation 4:

Equation 4. TPS61096A Eq_Vripple_SLVSDB2.gif

where

  • VRIPPLE refers to the output voltage ripple
  • tdelay is the internal comparator delay time, typical value 10 µs
  • COUT is effective output capacitance

For the output capacitor of VOUT pin, small ceramic capacitors are recommended. Place the output capacitor as close as possible to the VOUT and GND pins of the IC. If, for any reason, the application requires the use of large capacitors which cannot be placed close to the IC, the use of a small ceramic capacitor with a capacitance value of 1 μF in parallel to the large one is recommended. This small capacitor should be placed as close as possible to the VOUT and GND pins of the IC. The recommended typical output capacitor values are 10 μF (nominal value).

When selecting capacitors, the derating effect of the ceramic capacitor under bias should be considered. Choose the right nominal capacitance by checking the DC bias characteristics of the capacitor. In this example, GRM188R6YA106MA73D, a 10-µF ceramic capacitor with high effective capacitance value at DC biased condition, is selected for the VOUT rail. The performance is shown in the Application Curves section.

8.2.3 Application Curves

TPS61096A Switching_waveform_light_load_Vin=3.gif
Vin=3.6 V, Vout=12 V, Iout=30 mA
Figure 14. Switching Waveform at Heavy Load
TPS61096A Startup_by_Vin=3_6V_Vout=12V_Iout=2.gif
Vin=3.6 V, Vout=12 V, Iout=25 mA
Figure 16. Startup by VIN
TPS61096A Line_Transient_Vin=3_3V_3_6V_Vout=1.gif
Vin=3.0 V to 3.6 V, Vout=12 V, Iout=20 mA
Figure 18. Line Transient
TPS61096A Load_Transient_Vin=3_6V_Vout=12V_Iout_5_to_20mA.gif
Vin=3.6 V, Vout=12 V, Iout=5 mA to 20 mA
Figure 20. Load Transient
TPS61096A Level_Shift_Function_Vin=3_6V_Vout=12V.gif
LVI1 = LVI2 = 3.2 V, HVO1 = HVO2 = 12 V
Figure 22. Level Shifters Function
TPS61096A Swtiching_waveform_heavy_load_Vin=3.gif
Vin=3.6 V, Vout=12 V, Iout=2 mA
Figure 15. Switching Waveform at Light Load
TPS61096A Startup_EN_Vin=3_6V_Vout=12V_Iout=2.gif
Vin=3.6 V, Vout=12 V, Iout=25 mA
Figure 17. Startup by EN
TPS61096A Load_Regulation_Vin=3_6V_Vout=12V_I.gif
Vin=3.6 V, Vout=12 V, Iout=0 mA to 30 mA
Figure 19. Load Regulation
TPS61096A Line_Regulation_Vin=1_8V_to_4_2V_Vout=12V_Iout_20mA.gif
Vin=1.8 V to 4.2 V, Vout=12 V, Iout=20 mA
Figure 21. Line Regulation